The structure of the tetragonal phase of the A-site-substituted perovskite sodium bismuth titanate, Na0.5Bi0.5TiO3, has been determined by neutron powder diffraction at 698 K. The structure was refined in space group P4bm with a (= b) = 5.5191 (1), c = 3.9085 (1) Å, V = 119.055 (5) Å3, Z = 2 and Dx = 5.91 Mg m-3. The structure exhibits an unusual combination of in-phase (a0a0c+) tilts and antiparallel cation displacements along the polar c axis, which results in a new variant of the perovskite structure.
Supporting information
sodium bismuth titanate
top
Crystal data top
| Bi0.5Na0.5O3Ti | V = 119.06 (1) Å3 |
| Mr = 211.88 | Z = 2 |
| Tetragonal, P4bm | Dx = 5.91 Mg m−3 |
| Hall symbol: P 4 -2ab | ? radiation, λ = 1.595 Å |
| a = 5.5191 (1) Å | T = 698 K |
| c = 3.9085 (5) Å | ?, ? × ? × ? mm |
Data collection top
| 2θmin = 21.803°, 2θmax = 140.003°, 2θstep = 0.05° | |
Refinement top
| Rp = ? | ? data points |
| Rwp = ? | 39 parameters |
| Rexp = ? | |
| χ2 = 0.005 | |
Crystal data top
| Bi0.5Na0.5O3Ti | V = 119.06 (1) Å3 |
| Mr = 211.88 | Z = 2 |
| Tetragonal, P4bm | ? radiation, λ = 1.595 Å |
| a = 5.5191 (1) Å | T = 698 K |
| c = 3.9085 (5) Å | ?, ? × ? × ? mm |
Data collection top
| 2θmin = 21.803°, 2θmax = 140.003°, 2θstep = 0.05° | |
Refinement top
| Rp = ? | χ2 = 0.005 |
| Rwp = ? | ? data points |
| Rexp = ? | 39 parameters |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | Occ. (<1) |
| Na1 | 0.0 | 0.5 | 0.523 (4) | 0.05117 | .5 |
| Bi2 | 0.0 | 0.5 | 0.523 (4) | 0.07167 | .5 |
| Ti3 | 0.0 | 0.0 | 0.0 | 0.01591 | |
| O4 | 0.0 | 0.0 | 0.515 (4) | 0.04778 | |
| O5 | 0.270 (3) | 0.230 (3) | 0.026 (4) | 0.03766 | |
Atomic displacement parameters (Å2) top| | U11 | U22 | U33 | U12 | U13 | U23 |
| Na1 | 0.048 (5) | 0.048 (5) | 0.058 (5) | −0.004 (2) | 0.0 | 0.0 |
| Bi2 | 0.076 (4) | 0.076 (4) | 0.064 (8) | −0.003 (2) | 0.0 | 0.0 |
| Ti3 | 0.021 (2) | 0.021 (2) | 0.006 (4) | 0.0 | 0.0 | 0.0 |
| O4 | 0.068 (2) | 0.068 (2) | 0.008 (2) | 0.0 | 0.0 | 0.0 |
| O5 | 0.026 (1) | 0.026 (1) | 0.061 (2) | −0.012 (2) | 0.009 (4) | −0.009 (4) |
Geometric parameters (Å, º) top
| Na/Bi—O(1) | 2.7598 (1) | Na/Bi—O(2) | 2.6618 (1) |
| Na/Bi—O(2) | 2.8666 (1) | Na/Bi—Ti | 3.4343 (1) |
| Na/Bi—O(2) | 2.8822 (1) | Na/Bi—Ti | 3.3302 (1) |
| Na/Bi—O(2) | 2.6449 (1) | | |
| | | |
| Ti—Na/Bi—Ti | 111.919 (2) | Ti—Na/Bi—O(2) | 36.053 (1) |
| Ti—Na/Bi—Ti | 71.739 (1) | Ti—Na/Bi—O(2) | 143.977 (1) |
| Ti—Na/Bi—O(1) | 34.748 (1) | Ti—Na/Bi—O(2) | 88.951 (2) |
| Ti—Na/Bi—O(1) | 146.667 (1) | Ti—Na/Bi—O(2) | 90.778 (2) |
| Ti—Na/Bi—O(1) | 90.396 (1) | | |
Experimental details
| Crystal data |
| Chemical formula | Bi0.5Na0.5O3Ti |
| Mr | 211.88 |
| Crystal system, space group | Tetragonal, P4bm |
| Temperature (K) | 698 |
| a, c (Å) | 5.5191 (1), 3.9085 (5) |
| V (Å3) | 119.06 (1) |
| Z | 2 |
| Radiation type | ?, λ = 1.595 Å |
| Specimen shape, size (mm) | ?, ? × ? × ? |
| |
| Data collection |
| Diffractometer | ? |
| Specimen mounting | ? |
| Data collection mode | ? |
| Scan method | ? |
| 2θ values (°) | 2θmin = 21.803 2θmax = 140.003 2θstep = 0.05 |
| |
| Refinement |
| R factors and goodness of fit | Rp = ?, Rwp = ?, Rexp = ?, χ2 = 0.005 |
| No. of data points | ? |
| No. of parameters | 39 |
| No. of restraints | ? |
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![[Figure 1]](http://journals.iucr.org/b/issues/2000/03/00/bm0024/bm0024fig1thm.gif)
![[Figure 2]](http://journals.iucr.org/b/issues/2000/03/00/bm0024/bm0024fig2thm.gif)
